The term “caveman” is often used to refer to prehistoric humans – but when and where did early hominins first start dwelling in caves? A new paper published in Quaternary Science Reviews may have answered that question, updating previously reported results and showing that Wonderwerk cave in South Africa contains some of the earliest evidence for intentional fires and tools made by hominins.

Located between the towns of Danielskuil and Kuruman in South Africa, Wonderwerk cave – “wonderwerk” meaning “miracle” in Afrikaans – extends 140 meters (459 feet) deep into the Kuruman Hills. The site doesn’t actually contain any hominin fossils, but plant and animal remains as well as archaeological artifacts mean that it is a key site for our understanding of the Earlier Stone Age in the region.

The artifacts in the cave include tools including those of the Oldowan style, simple stone tools used by early humans during the Lower Palaeolithic period 2.6 million to 1.7 million years ago. The authors of the paper note that Olowan tools in South Africa can be traced back to the same time period of fossils of multiple early hominins, including early Homo, Paranthropus, and Australopithecus sediba.

The lead author of the new paper Professor Ron Shaar from the Hebrew University of Jerusalem’s Institute of Earth Sciences said in a statement that "We can now say with confidence that our human ancestors were making simple Oldowan stone tools inside the Wonderwerk Cave 1.8 million years ago.

“Wonderwerk is unique among ancient Oldowan sites, a tool-type first found 2.6 million years ago in East Africa, precisely because it is a cave and not an open-air occurrence."

The fact that Wonderwerk is not open-air also makes it significant in dating the first intentional use of fire by early humans. While other examples of early fires potentially linked to early humans exist, the fact that they are out in the open means that wildfires could be the cause rather than deliberate actions by early humans. The researchers behind this new paper were able to date the deliberate use of fire in the cave to one million years ago.

The researchers came to these conclusions by studying a 2.5-meter (8.2-foot) thick sedimentary layer 30 meters (98.4 feet) into the cave. The samples used came from profiles excavated in the 1970s and 1980s. Paleomagnetism and burial dating were used to analyze these samples.

“Quartz particles in sand have a built-in geological clock that starts ticking when they enter a cave,” explained co-author Professor Ari Matmon, Director of the Institute of Earth Sciences. “In our lab, we are able to measure the concentrations of specific isotopes in those particles and deduce how much time had passed since those grains of sand entered the cave,"

"We carefully removed hundreds of tiny sediment samples from the cave walls and measured their magnetic signal," added Professor Shaar. "Our lab analysis showed that some of the samples were magnetized to the south instead of the north, which is the direction of today's magnetic field. Since the exact timing of these magnetic "reversals" is globally recognized, it gave us clues to the antiquity of the entire sequence of layers in the cave."